The invention relates to high speed lenses or objectives, useful particularly but not exclusively in photography. Many forms of such lenses are known in the art. The lenses of the present invention are of the type sometimes referred to as quasi-telephoto lenses, having a very short and compactly constructed rear member, the lens as a whole being a relatively high speed lens with a relative aperture in the range of about f/2 to f/1.4.
The lenses of the present invention are intended particularly for installation in a 35 millimeter reflex camera. The present invention provides a sufficiently great back focus (axial distance from the rear vertex of the rear element of the lens to the focal plane or film plane when focused at infinity) to allow room for swinging a reflex mirror, as necessary in a camera of this type.
Also, the lens construction according to the present invention provides a central space between the front member and the rear member of the lens, sufficiently great to permit the installation at this point of a diaphragm (preferably a diaphragm of adjustable aperture, such as a conventional iris diaphragm), or an objective shutter, or both a diaphragm and a shutter, if desired. Of course the lens of the present invention is not limited to use with an objective shutter (often also called a central shutter, or a lens shutter), and it is immaterial so far as the present invention is concerned, whether the camera associated with this lens is equipped with an objective shutter or with a focal plane shutter.